2、知道分布式锁吗？有哪些实现方案？ 你谈谈对redis分布式锁的理解

Base案例

1、建Module

2、改POM

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.sl</groupId>
    <artifactId>boot_redis01</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>boot_redis01</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <spring-boot.version>2.3.0.RELEASE</spring-boot.version>
    </properties>

    <dependencies>
        <!--默认是lettuce客户端-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>
        <!-- redis依赖commons-pool 这个依赖一定要添加 -->
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-pool2</artifactId>
        </dependency>


        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>com.sun.mail</groupId>
            <artifactId>jakarta.mail</artifactId>
            <version>1.6.5</version>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring-boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>



        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

3、写YML

server:
  port: 1111

spring:
  redis:
    port: 6379
    host: 192.168.80.16
    lettuce:
      pool:
        max-active: 8 # 连接池最大连接数（使用负值表示没有限制）
        max-idle: 8 # 连接池中的最大空闲连接
        min-idle: 0 # 连接池中的最小空闲连接
        max-wait: 1000 # 连接池最大阻塞等待时间（使用负值表示没有限制）
      shutdown-timeout: 100
    password: root

3、业务类
config

@Configuration
public class RedisConfig {

/**
 * 保证不是序列化后的乱码配置
 */
    @Bean
    public RedisTemplate<String, Serializable> redisTemplate(LettuceConnectionFactory connectionFactory){
        RedisTemplate<String, Serializable> redisTemplate = new RedisTemplate();
        redisTemplate.setKeySerializer(new StringRedisSerializer());
        redisTemplate.setValueSerializer(new GenericJackson2JsonRedisSerializer());
        redisTemplate.setConnectionFactory(connectionFactory);
        return redisTemplate;
    }
}

controller

@RestController
public class GoodController {

    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    @Value("${server.port}")
    private String serverPort;

    @GetMapping("/buy_goods")
    public String buy_Goods(){

        String result = stringRedisTemplate.opsForValue().get("goods:001");
        int goodsNumber = result == null ? 0 : Integer.parseInt(result);

        if (goodsNumber > 0){
            int realNumber = goodsNumber - 1;
            stringRedisTemplate.opsForValue().set("goods:001",realNumber + "");
            System.out.println("你已经成功秒杀商品，此时还剩余：" + realNumber + "件"+"\t 服务器端口: "+serverPort);
            return "你已经成功秒杀商品，此时还剩余：" + realNumber + "件"+"\t 服务器端口: "+serverPort;
        }else {
            System.out.println("商品已经售罄/活动结束/调用超时，欢迎下次光临"+"\t 服务器端口: "+serverPort);
        }
        return "商品已经售罄/活动结束/调用超时，欢迎下次光临"+"\t 服务器端口: "+serverPort;
    }

}

V2.0

没有加锁，并发下数字不对，出现超卖现象，于是加上